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ESOS Phase 4 compliance
Who qualifies.What is audited.What is filed.
In short
ESOS applies to large undertakings: 250 or more UK employees, or turnover above £44m together with a balance sheet total above £38m. Your position on 31 December 2026 decides Phase 4 scope, and the notification is due by 5 December 2027. If any UK entity in your group meets the test, every UK entity is in scope.
What this does not do. An assessment does not reduce a bill on its own. It produces a quantified list of savings, and the reduction comes from acting on that list.
Who this is for
Organisations that are, or may be, large undertakings, and groups where one subsidiary could bring the rest into scope.
Finance and company secretarial teams usually hold the qualification figures, and property or facilities teams hold the consumption data. ESOS needs both, which is why it is often started later than it should be.
The regulatory detail, with the dates, thresholds and the five Phase 4 requirements set out in full, is in the ESOS Phase 4 sheet.
What we examine
- The corporate group structure, entity by entity, because one qualifying entity brings the rest in.
- Headcount, turnover and balance sheet position against the large undertaking test.
- Total energy use across buildings, transport and industrial processes for a twelve-month reference period that includes the qualification date.
- Half-hourly, AMR and invoice data for each supply, so the measurement rests on records rather than estimates.
- Any previous ESOS action plan, since progress against earlier commitments now has to be reported.
The process
01
Establish scope
We test each UK entity against the qualification thresholds and set out, in writing, who is in scope and who is not.
02
Measure total energy
Energy use is assembled across buildings, transport and processes for the reference period, from meter data and invoices.
03
Audit the significant consumption
95 per cent of total consumption has to be covered for Phase 4, raised from 90 per cent, and audited by or signed off under an approved lead assessor.
04
Quantify the opportunities
The audit sets out cost-effective savings with the energy and cost figures attached, rather than a list of generic measures.
05
Action plan and notification
An action plan is produced, progress against previous commitments is reported, and the notification is filed by the deadline.
06
Act on the list
The audit is the valuable part. We would rather help you act on the quantified savings than help you file them.
What you receive
Evidence kept in a form an auditor can follow: the data used, the date it was taken, the source it came from and the calculation applied to it.
- A written scope determination for each UK entity.
- The energy measurement for the reference period, with its sources.
- The audit and the quantified savings, with costs and payback where they can be established.
- The action plan, and the progress report against earlier commitments.
- The compliance notification and its filing record.
- What we can and cannot control, stated plainly alongside each recommendation.
What this does not do
- We cannot make you compliant for a phase whose deadline has passed, and we will not present a late notification as anything other than late.
- Display Energy Certificates and Green Deal Assessments are no longer valid compliance routes, so an existing certificate does not settle the obligation.
- Full Phase 4 guidance is expected in early 2027. Where detail is still to come we say so rather than fill the gap.
The first review costs nothing. Anything after it is quoted and agreed in writing before it starts.
Questions
- Who has to comply with ESOS?
- A large undertaking, tested at 250 or more UK employees on its own, or turnover above £44m together with a balance sheet total above £38m. Your position on the qualification date of 31 December 2026 decides whether you are in scope for Phase 4.
- What is the ESOS Phase 4 deadline?
- 5 December 2027. The compliance notification must reach the Environment Agency, or the devolved nation equivalent, by then, through MESOS.
- We did not qualify last time. Are we safe?
- No. Qualification is assessed afresh each phase, so not qualifying before does not carry forward. An organisation that missed the Phase 3 snapshot on 31 December 2022 may qualify now after four years of growth.
- Does one subsidiary bring the whole group in?
- Yes. If any single UK entity in a corporate group meets the test, every UK entity in that group is brought into scope, including ones individually well below the threshold. This is the point most often missed.
- Is ESOS the same test as SECR?
- No. ESOS is 250 or more employees on its own, or both financial thresholds together. SECR is two of three thresholds. The same company can sit inside one regime and outside the other, so both need checking on your actual figures.
- What does ESOS support cost?
- The initial review, which establishes whether you are in scope and what data you hold, costs nothing. The assessment work itself is quoted and agreed in writing before it starts, and the lead assessor requirement is set out in that quotation.
Read the detail
Related: SECR reporting, all compliance work and commercial energy audits.
How to check this
Each claim on this page is answered by something you can read for yourself. Nothing below states a figure; it names the document or register the claim is held against.
Point 01
We hold a Level 1 Letter of Authority only
The authority wording sets out what we may do with your data and states that we cannot sign a contract on your behalf. Read it before you sign it.
Point 02
How we are paid is agreed in writing before you sign
Our margin or management fee is stated in the terms that accompany a recommendation, and nothing is added afterwards.
Point 03
Every figure we quote carries a dated source document
Records state the figure, what it is measured against, the document it is taken from and the date on that document. Records still held anonymous are labelled as such.
Point 04
Compliance work is held against the current legislation
Each obligation is recorded with the rule it comes from and the deadline it carries, in an evidence pack an auditor can follow.
Point 05
We work to a published code of conduct
Our obligations as a third party intermediary, and what you can hold us to, are set out in full.
Ask about ESOS
Put a question about the scheme and get a plain-English explanation drawn from what we already publish, with the source you can check named. It reads our compliance pages and sheets, and nothing else.
Answers come from published pages and are not a quotation, a contract or legal advice. Questions are recorded so we can see what buyers are asking, and are covered by our privacy notice. The first review costs nothing; anything after it is quoted and agreed in writing.